Fork#41597: std::remquo does not yield the proper result for the quotient
Open Date: 2021-02-17 21:25
Last Update: 2021-02-24 21:15
URL for this Ticket:
https://osdn.net//projects/mingw/ticket/41597
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Last Changes/Comment on this Ticket:
2021-02-24 21:15 Updated by: keith
Comment:
Addendum To keith
I've fixed it, ... I'll update the patch, to reflect the correction, shortly.
Done. The difference, w.r.t. the preceding patch, is effectively:
$ hg diff diff --git a/mingwrt/mingwex/math/remquo_generic.sx b/mingwrt/mingwex/math/remquo_generic.sx --- a/mingwrt/mingwex/math/remquo_generic.sx +++ b/mingwrt/mingwex/math/remquo_generic.sx @@ -90,12 +90,12 @@ */ .globl _remquol .def _remquol; .scl 2; .type 32; .endef _remquol: - fld DWORD ptr 4[esp] /* FPU TOS = x */ - fld DWORD ptr 16[esp] /* FPU TOS = y, x */ + fld TBYTE ptr 4[esp] /* FPU TOS = x */ + fld TBYTE ptr 16[esp] /* FPU TOS = y, x */ mov edx, DWORD ptr 28[esp] /* EDX = *q */ /* Hand off the preloaded register set, to the shared computational * back-end routine, to... */
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Ticket Status:
Reporter: avhaecke
Owner: keith
Type: Issues
Status: Open [Owner assigned]
Priority: 5 - Medium
MileStone: (None)
Component: WSL
Severity: 5 - Medium
Resolution: None
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Ticket details:
Context :
This problem was encountered with gcc on MinGW in the following version :
gcc.exe (MinGW.org GCC-6.3.0-1) 6.3.0
Description :
The following code :
double numer = 90.1 ; double denom = 90 .0 ; int quot ; double result = std::remquo(numer, denom, ") ; std::cout << "result " << result << std::endl ; std::cout << "quot " << quot << std::endl;should yield :
result 0.1
quot 1
As is expected from std::remquo, quot has a magnitude which should be congruent (modulo 2 to the nth) to the magnitude of the integral quotient of x/y, n being greater or equal than 3.
However with gcc 6.3.0, on MinGW, the above instructions yield :
result 0.1
quot 0
On another version of gcc (gcc 4.9.1 2014), the expected behavior is encountered.
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